(1) Field of the Invention
This invention relates to blowers used on high efficiency furnaces and, more particularly, to an exhaust interface formed on a discharge pipe of a blower housing.
(2) Background of the Invention
Blowers are commonly used in high efficiency furnaces (e.g. 90% efficiency) for drawing combustion air into the furnace and for removing exhaust gases from the furnace. Generally, these blowers are located downstream of a combustion chamber or combustion tubes in the furnace, depending upon the style of furnace, and propel exhaust gases out the furnace through an exhaust pipe that vents to outside atmosphere.
FIGS. 1 and 2 show the typical arrangement of a blower 20 of the prior art. The blower 20 includes a blower motor 22 and a blower housing 24. In FIG. 1A, the blower motor has been removed from its center mount 26 on top of the blower housing 24 to show greater detail of the blower housing 24. The blower housing 24 has an upstanding annular wall 28 extending between a top piece 30 and a bottom piece 32. The top piece 30 is molded to include the center mount recess 26 to receive the blower motor 22. The annular wall 28, top piece 30, and bottom piece 32 form a volute 34 for the blower housing 24. An impeller 22, operably connected to a shaft of the blower motor 22 rotates in the volute 34 when the blower 20 is energized to draw exhaust gases through an inlet hole (not shown) in the center of the bottom piece 32. The gases are then compressed in the volute 34 and directed into a discharge pipe 36 that extends outward and away from the volute 34.
FIG. 2 shows the general arrangement of the blower installed in a furnace 38. The blower is mounted on a blower mounting surface 40 on the furnace 38 where the inlet hole (not shown) of the blower housing 24 is positioned to allow the impeller to draw exhaust gases directly from the combustion chamber or combustion tubes (not shown) into the blower housing 24. The discharge pipe 36 is coupled to an exhaust pipe 42 using a double booted rubber gasket 46 to vent the exhaust gases to atmosphere. In the prior art, the blower housing 24 and exhaust pipe 42 are commonly made from a polypropylene or polyvinyl chloride (PVC) plastic material.
Greater detail of the double booted gasket 46 of the prior art is shown in FIG. 1B. The double booted rubber gasket 46 is a cylindrically shaped tubular member with first and second ends 48,50. The first end 48 has a first internal annular groove 52 that forms a first annular socket 54 that fits on a boss end 56 of the discharge pipe 36 of the blower housing 24. To secure the double booted rubber gasket 46 to the discharge pipe 36 of the blower housing 24, a first hose clamp 58 is typically used. The second end 50 of the double booted gasket 46 has a similar arrangement with a tubular insert 60 concentrically disposed within the gasket 46 to form a second internal annular groove 62. The exhaust pipe 42 is received within the second internal annular groove 62 and is secured to the double booted gasket 46 by tightening a second hose clamp 64. The second internal annular groove 62 has a groove root 66 with baffles 68 to collect condensate that is entrained in the exhaust gas stream. This condensate is collected at the root 66 and is removed from the double booted gasket 46 through drain portals 70 on the sides of the double booted gasket 46 that communicate with the groove root 66.
The use of the double booted gasket 46 has several drawbacks. The double booted gasket 46 is a complex part that must be manufactured in an intricate molding process. Because the gasket 46 is an added part to be fitted between the blower housing 24 and the exhaust pipe 42, it complicates the installation process. Further, as is readily apparent to those of skill in the art, a pair of pipe clamps must be aligned and screwed tight to complete the installation which takes some time and careful attention. The added part also increases the expense of the blower 20 and the installation of the blower 20 on the furnace 38.
The double booted gasket 46 must also be made from a relatively strong material that must withstand industry standards for mechanical strength and exhaust system integrity. Generally, in this application on a high efficiency furnace, the double booted gasket 46 must be able to maintain its connection to the discharge pipe 36 with a 25 ft-lb torque exerted on the exhaust pipe 42 (the xe2x80x9ctwistxe2x80x9d condition). The gasket 46 must also maintain its connection to the discharge pipe 36 with a 50 lb. parallel pull out force exerted axially along the exhaust pipe 42 (the xe2x80x9cpull-outxe2x80x9d condition). Because the double booted gasket 46 has one hose clamp connection with the discharge pipe 36 and another hose clamp connection with the exhaust pipe 42, the double booted gasket 46 has two points for failure. Thus, the gasket 46 is susceptible to failure at either one of these two connections which represent the most likely point of failure.
What is needed in the art is a method of improving the connection between the blower housing 24 and the exhaust pipe 36 such that the industry standard mechanical tests for strength and exhaust system integrity are maintained while providing a less expensive part with an easier install procedure.
It is, therefore, an object of the present invention to provide an exhaust interface for a blower that simplifies the connection between the blower housing and the exhaust pipe while meeting the requisite industry standards for strength and exhaust system integrity.
The blower of the present invention includes a blower housing and a blower motor. The blower housing has an impeller and a discharge pipe for directing exhaust gases out and away from the blower. The discharge pipe has a first end that is formed adjacent the housing and an opposite second end that is spaced from the housing, or volute. The second end includes an exhaust flange with an annular socket and a plurality of resilient teeth extending axially outwardly from the second end and circumferentially spaced around the annular socket.
The blower includes an exhaust fitting that has an outer cylinder with a front end and an axially opposite back end, and a generally tubular insert disposed within the outer cylinder. An annular back wall extends between the outer cylinder and tubular insert. The tubular insert is attached to the annular back wall at the back end of the outer cylinder such that the tubular insert extends outward and away from the back wall and through the front end of the outer cylinder. The tubular insert forms an annular groove in the front end of the exhaust fitting.
The exhaust fitting is received in the annular socket of the exhaust flange, and the exhaust pipe is received in the annular groove. A clamping means such as preferably a pipe clamp for radially compressing the plurality of circumferentialy spaced teeth on the exhaust flange may be used to secure the exhaust pipe within the exhaust fitting and the exhaust fitting within the annular socket of the exhaust flange.
The exhaust fitting and exhaust flange are preferably keyed so that the exhaust fitting may be assembled in the annual socket on the exhaust flange in only one circumferential orientation. The exhaust flange preferably has an integral drain for removing condensate in the exhaust gases. In this configuration, the exhaust fitting may have a guttering system adjacent the back wall of the annular groove that directs condensate from the exhaust pipe into the drain on the exhaust flange. Preferably, each of the circumferentialy spaced teeth has a proximal end which is cantileverly attached to the second end of the discharge pipe and a distal end which is spaced away from the proximal end. The distal end of each of the teeth may have an annular ridge that extends radially outward and engages a portion of the clamping means to prevent the clamping means from sliding off the teeth when the clamping means is tightened around the teeth. The clamping means is preferably a pipe clamp, as in the prior art. The discharge pipe, exhaust flange, and volute of the blower housing are preferably monolithically constructed as the exhaust flange may be molded as a mold insert as the blower housing is molded.